Successful computer software applications, in particular computer games, often result in the wish of the users of such software applications to enhance the capabilities of the software applications by using additional add-on data files, such as additional level files for computer games, additional map files for navigation programs, additional font files for word processing programs or other extension files. Since the economic success of such software applications often can not be foreseen, such additional add-on files are often not included into the original software application. The market for selling such additional add-on files, which have been developed by other programmers and are supplied by other suppliers than the original developers of the software application and the original suppliers is increasing. Nowadays such additional add-on data files often are provided via the Internet. Since the programmers, creators and suppliers of such add-on files also want to be reimbursed for their efforts, such add-on data files have to be protected against copying.
Such copy protection for add-on data files is not easy to achieve. One possibility is that the programmer of the original software application has to implement the access code layer, e.g. some sort of decryption/encryption algorithm, within the original software application, which is cumbersome and normally programmers of software applications, in particular computer games, are not experts in programming copy protection software. Additionally time constraints in developing computer games are quite severe, so that the additional effort to include a copy protection for add-on data files should be prevented. Furtheron, since the original programmer and original supplier are different from the programmers and suppliers of add-on data files, they are less motivated to include such a copy protection into the original software application.
In another approach the add-on data files are encrypted. A user who wants to use such additional add-on data files gets a decryption key after having paid for being allowed to use the add-on data file. However, after the add-on data file has been decrypted with the help of the decryption key, it is available for further unauthorized copying and distributing, thereby reducing the income for the programmer and supplier of the add-on data files.
It is an object of the present invention to provide a method for managing access to at least one add-on data file, which is used by a software application, that is easy to handle by a publisher of the software application and that provides an efficient protection against unauthorized copying of such add-on data files.
It is further object of the present invention to provide a system for managing access to at least one add-on data file, which is used by a software application, that is easy to use by a programmer of the software application, that provides an efficient protection against unauthorized copying of such add-on data files that is convenient to use by a user of such add-on data files.